1. Field of the Invention
The present invention relates to a control apparatus of a storage unit and to a method of controlling the control apparatus of the storage unit.
2. Description of the Related Art
A computer system can add new functions by changing a control program even after initiating operation. Ordinarily, the device is restarted in order to install a new control program in the device.
However, the system cannot be stopped in a computer system where continuous operation is demanded 24 hours a day 365 days a year.
For this reason, in a case where a control program of a control apparatus of a storage unit in a computer system is to be changed, technology has conventionally been proposed for changing the control program without stopping the input/output of data (e.g., see Japanese Patent Application Laid-Open Publication No. Hei7-306844).
To cite an example of another specific method, there is a method where software for managing a bus is installed in a server and the inflow of commands to a control section in which is installed a microprocessor that replaces the control program is temporarily prohibited. Because a plurality of buses are managed by this application, a storage control apparatus can receive commands through the bus connected to the control section whose control program is not being in the middle of being replaced. In other words, the input/output of data from the server is not completely stopped.
Moreover, another method is known where, even if a command is received from the server, the control section whose control program is in the middle of being replaced issues a retry request to the server and causes the server to wait until the replacement of the control program ends.
In this conventional technology, the fact that there are a plurality of buses that transfer data from the computer to the control apparatus of the storage unit is used to change the control program without stopping the overall input/output of data from the computer. However, the input/output of data from the computer is stopped with respect to the data transfer bus relating to the changing of the control program. For this reason, it has been necessary for the computer to conduct data input/output by bypassing this data transfer bus.